1. Field of the Invention
This invention relates generally to measurement and data acquisition systems and, more particularly, to PXI Express controller design.
2. Description of the Related Art
In meeting the demand for increased functionality coupled with reduced cost/time-to-market in instrumentation design, most instrumentation systems have begun to leverage existing, off-the-shelf technologies. The PCI Express eXtensions for Instrumentation (PXI Express)—introduced in 2005 by National Instruments—is one of several electronic instrumentation platforms in current use, and represents a modular instrumentation platform that leverages existing technology to deliver high performance and low cost modular instrumentation. PXI Express is ideally suited for building electronic test-equipment and/or automation systems, and is based on industry-standard computer buses complemented with extra features to facilitate electronic test. PXI Express affords great flexibility in building test equipment and/or automation systems to exact requirements, often fitted with custom software for managing the entire system.
PXI Express was conceived for measurement and automation applications that typically require high-performance and a rugged industrial form-factor. PXI Express also allows for module selection from a large number of vendors, with the modules easy integrating into a single PXI Express system. A typical 3U PXI Express module measures approximately 4×6 inches in size, and a typical 8-slot PXI Express rack is about the size of a small toaster oven. Overall, PXI Express uses PC-based technology as part of an industry standard governed by the PXI Systems Alliance (PXISA), ensuring standards compliance and system interoperability. PXI Express modules are available for a wide variety of test, measurement, and automation applications, from switching modules to high performance microwave vector signal generation and analysis instruments.
PXI Express modules are typically designed to implement specific functions, such as analog signal capture, RF signal analysis, and/or waveform generation. PXI Express modules that provide instrument functions usually plug into a PXI Express chassis that may include its own controller running an industry standard Operating System (e.g. Windows XP, Windows 2000, and/or Linux), or a PCI Express-to-PXI Express bridge that provides a high-speed link to a desktop PC controller. Similarly, multiple PXI Express racks may be linked together with PCI Express bridge cards to build very large systems such as multiple source microwave signal generator test stands for complex ATE applications.
Many of the PXI Express Controllers offered by National Instruments (NI) are typically turned on and off by the use of a chassis power button on the front of a PXI Express chassis. The chassis power button is generally an input signal from a mechanical momentary switch indicating that an operator of a PXI Express chassis wants to change the system on/off state. To change the system on/off state, the chassis power button will assert a signal to the controller indicating that it wants to change state. The circuitry that detects this signal is typically powered from the chassis auxiliary power. Auxiliary power refers to power that is always provided by the chassis as long as the chassis is plugged into an AC outlet. The controller will in turn use the on/off state to control the chassis on/off state. To change the chassis on/off state, a signal may be asserted indicating to the chassis that the main power supply needs to be turned on or off. The main power supply can provide the power necessary to turn on the controller.
In certain cases, however, some chassis may not be configured with a chassis power button. Chassis that do not implement a chassis power button would need to be provided with some alternate means to turn the chassis on. This may typically be accomplished through a mechanical power switch, which would be used to turn on/off the main power supplies that are comprised in the chassis. In some cases the chassis may not be configured to provide auxiliary power, requiring that the auxiliary power be connected to the main power supply. If the chassis did not provide auxiliary power, the use of a chassis power button would not be possible. Therefore the chassis would need to be turned on/off using a mechanical power switch in the same manner as previously described.
In the cases described above, the controller is typically expected to have the capability to turn on the chassis main power supply, preferably without user intervention. Another requirement may be for the chassis main power supply to remain turned off when a controller is inserted into a chassis that is plugged into an AC outlet. In other words, the controller would be expected to not turn on the main power supply. If the controller is already plugged into the chassis when the chassis is plugged into the AC outlet, the chassis main power supply may also be expected to remain turned off.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.